This description relates to operation of electronic systems in particular surge protection of circuits and systems.
One troublesome source of voltage surges result from lighting strikes. Lighting is a perplexing source of surges because a lighting strike can induce very high energy into a circuit at a very high rise time (on the order of micro-seconds). Microelectronic Integrated Circuits (MIC's) especially those that operate with low voltages and/or have field effect transistors on input lines are also susceptible to damage from electrostatic discharge such as static electricity that comes from improper handling and voltage surges.
Underwriter Laboratories, Inc. (UL) has promulgated standards UL-1076 (Proprietary Burglar Alarm Systems) and UL-294 (Access Control) to define a level of surge suppression performance expected for high security facilities. These UL standards define test requirements of multiple surges that are injected into all I/O ports on a device. The UL Transient Test Requirements (as defined in UL-1076) tests are generally set out below, in relevant part:                44.4.3 For this test, each input/output circuit is to be subjected to five different transient waveforms having peak voltage levels in the range of 100 to 2400 volts, as delivered into a 200-ohm impedance. A transient waveform at 2400 volts shall have a pulse rise time of 100 volts per microsecond, and a pulse decay duration of approximately 80 microseconds, which is generating an energy level of over 1.2 joules. Other applied transients shall have peak voltages representative of the entire range of 100 to 2400 volts, with pulse durations from 80 to 110 microseconds, and energy levels not less than 0.3 joule or greater than 1.2 joules and to a maximum of approximately 1.2 joules. The transient pulses are to be coupled directly into each individual input/output circuit conductor to earth ground and to all combinations within a connector of the equipment under test.        44.4.4 The equipment is to be subjected to 60 transient pulses induced at a maximum rate of six pulses per minute as follows:        a) Twenty pulses (two at each transient voltage level specified in 44.4.3) between each input/output circuit lead or terminal and earth ground, consisting of ten pulses of one polarity, and ten of the opposite polarity (total of 40 pulses) and        b) Twenty pulses (two at each transient voltage level specified in 44.4.3) between any two input/output circuit leads or terminals consisting of ten pulses of one polarity and ten pulses of the opposite polarity.        